A hybrid vehicle equipped with an engine and a motor generator commonly employs a high potential of a few hundreds volts for contributing to the size reduction and the high efficiency of the motor generator as well as a low voltage of 14 V (or 12 V) for power supply to electric components which are used in an existing combustion engine vehicle. Consequently, a high voltage battery for providing a high voltage of a few hundreds volts is provided in addition to a common 14-V (12-V ) low-voltage battery. Also, a medium voltage of 42 V is sometimes utilized for motors consuming a large amount of power, such as an electric power steering motor and an air conditioning compressor motor. In general, a medium voltage of 42 V is generated as a result of stepping down a high potential by a DC/DC converter and no specific medium voltage battery, is provided.
Disclosed in Prior Art is an invention for responding to the back electromotive force of an electric motor in an electrical power steering device.
Prior Art: JP 2002-321631 A is incorporated herein by reference.